<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        alert("放在head中的脚步先执行了")
    </script>
</head>
<body>
    <h1>文档在脚步执行结束后加载</h1>
</body>
</html>